Recovery of oils



March 30, 1965 J. w. SLOVER 3,175,969

RECOVERY OF OILS Filed Jan. 11, 1962 USED SEAL LIQUID l2 II VACUU 5 VAPOR] 6 il 3? PSIA -10 "T. "A4 -$EAL LIQUIDBEE LIQUID WET OIL P FEED3 l 30 PsIA 7 e 9 DRY oIL YIELD H F/G.

GASES IS TO FLARE I I6 ACCUM. l7 z 1 I ;/\CRACKED GASOLINE USED SEAL A OIL) IGHT HYDROCARBON VAPORS 1 x L AND WATER vAPoR NLIGHT CYCLE 2'\-- l4 OIL --T' VACUUM HEAVg cYcLE PUMP 5 VAPOR 6 FEED L SEAL I 3 oIL f- I 1- DRY FUEL LIGHT CYCLE STEAM 4' GAS oIL PI oDucT P w IBJIQOTTOMS 8? PRODUCT INVENTOR. HQ 2 J.W.SLOVER I A TTORNE KS United States Patent 3,175,969 REQGVERY @F 8H5 .lames W. Slover, Phillips, Tern, assignor to Fhiilips setroleum Eompany, a corporation of Delaware Filled Ian. ill, 1962, Ser. No. 165,493 2 t'llaims. (6i. 2ti8-I$'7) This invention relates to recovery of oils. In one of its aspects, the invention relates to an operation where an oil is stripped under reduced pressure conditions and wherein the stripped oil is used as a seal for the zone which produces the reduced pressure. In another of its aspects, the invention relates to an apparatus comprising, in combination, a vacuum-stripping means, means in combination with said vacuum-stripping means for creating a reduced pressure therein, means in combination with said vacuum-stripping means for removing vacuumstripped liquid therefrom, and means for passing at least a portion of vacuum-stripped liquid thus removed to said means for producing a reduced pressure in said vacuums'rripping means as a sealing fluid therefor.

In the recovery of oils from hydrocarbon cracking operations, for example, from the cracking of a heavy hydrocarbon oil to produce fuel oil, intermediate distillate oils, and gasoline fractions, there is ordinarily employed a reduced pressure stripping operation to remove light hydrocarbons and, in some cases, water vapor from the intermediate oils or a light cycle oil which is desired to be obtained. Ordinarily, steam has been used to motivate an ejector means or vacuum-producing zone. This steam is then passed into the stripper wherein the oil has been preliminarily stripped with steam. It has now been conceived that the intermediate stripper zone wherein oil is stripped with steam can be eliminated if a vacuum pump is used to produce the desired low pressure and, further, that the stripped oil can be used as a seal oil for the vacuum pump. This stripped oil has the advantage of having a Very low vapor pressure and can be used in any desired amount, thus eliminating the use of steam and steam jets entirely, the capacity of which may not be great enough and which, even if its capacity is great enough, uses large quantities of steam which must be disposed of in the operation. The use of too much steam in existing units overloads the overhead condensing systems thereof.

It is an object of this invention to recover oils. It is another object of this invention to recover intermediate oils which have been stripped of light hydrocarbons and any water vapor which they may contain. It is a further object of this invention to provide a combination operation in which a vacuum-producing pump is used. It is a further object of this invention to eliminate a steamstripping operation in the production of light or similar cycle oils. A still further object of the invention is to provide a sealing fluid for a vacuum-producing means or zone.

Other aspects, objects and the several advantages of this invention are apparent from a study of this disclosure, the drawing and the appended claims.

According to the present invention, there is provided a method for the recovery of a reduced pressure stripped oil fraction from a stream of oil containing the same which comprises passing said stream of oil into a zone of reduced pressure, maintaining the reduced pressure on said zone, employing a vacuum-producing zone, removing vacuum-stripped oil from said reduced pressure zone as a product of the method and passing a portion of said reduced pressure stripped oil to the vacuum-producing zone as a low vapor pressure seal oil therefor.

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Referring now to the drawing, FIGURE 1 shows an operation in diagrammatic manner in which an oil is taken from a mid-portion of a fractionation column and passed to a reduced pressure stripping zone, the reduced pressure on which is maintained employing a vacuum pump, the seal liquid of which is obtained from the reduced pressure zone. FIGURE 2 shows a combination of the general operation of FIGURE 1 with the overall operation of recovering oils from a cracked oil stream obtained in the production of cracked gasoline product oils and heavier fuel oil.

Referring now to FIGURE 1, there is taken from fractionator 2 by pipe 3 a stream of light cycle oil which it is desired to strip of lighter hydrocarbons and water vapor contained therein. The oil in 3 is passed to reduced pres sure vessel l wherein it is subjected to a reduced pressure drawing on vessel 4 by means of pump 5 and conduit 6. Stripped light cycle oil is passed by 7 to pump 8 and from the system at 9. A portion of the light cycle oil is passed by It? to pump 5 and thence to fractionator Z by 11. If desired, there can be interposed in pipe It) a heat exchanger to adjust the temperature of the light cycle oil to that most desirable for operating the vacuum pump. Thus, the oil in 1.0 can be either heated or cooled to trim its temperature to a desired one. In this embodiment, the temperature of the seal liquid or light cycle oil which is cycled through vacuum pump 5 will be in the range 50- 250 F. From pump 5, light hydrocarbon and any water vapor are passed by 12 to fractionator 2. It will be seen that, according to the invention, there is provided in situ a seal liquid of low vapor pressure adapted to seal vacuum pump 5 and that this seal liquid is constantly renewed and disposed of into fractionator 2. This means that there is no loss of seal liquid and that there is at all times a low vapor pressure seal liquid available in the pump for its operation. Thus, any vapors absorbed by the seal liquid in pump 5 are passed by 11 to tower 2. The low vapor pressure of the seal liquid in pump 5 is maintained by its constant renewal, as indicated.

Referring now to FIGURE 2, there is shown an overall operation wherein there is fed a synthetic cracked feed 1 to fractionator tower 2. In fraotionator tower Z the oil is separated into at least the following fractions: a :fuel oil removed at 13, a heavy cycle removed at 14, a light cycle oil removed at 3, and an overhead removed at 15. The overhead is condensed to the extent possible, usually with condense-r water, uncondensed gases are removed for further treatment, as in polymerization, alkylation, etc., which are operations well known in the refinery, and gasoline liquid is, in part, recycled to assist in the operation of tower 2 while production quantities are recycled by 16 while cracked gasoline is removed from the system by 17. The light cycle oil removed at 3 now passes to vacuum stripper 4 and the remainder of the operation is as indicated in connection with FIGURE 1. The numbers in FIGURE 2 from 1 to 12, inclusive, correspond to the numbers in FIG. 1. It will be seen from FIGURE 2 that light hydrocarbons and water vapor are returned by pipe 12 and that these light hydrocarbons are ultimately recovered as a portion of the cracked gasoline containing overhead. Further, any light cycle oil which has been entrained through pipe 6, vacuum pump 5 and returned by 12 will reappear again in pipe 3 and, therefore, ultimately find its way to pipe 9 as a product of the system. In some operations, stripping gas 4, e.g., a fuel gas, is used in vessel 4 to assist in light component removal. Further, in some operations, cooler 6' in conduit 6, and cooler 8 in the seal oil line are used to adjust the temperatures of the components in these streams, as desired.

3,1 3 And when fuel @gas 4' is used, at least a portion of the vacuum pump 5 efiluent 12 is diverted by way of conduit 12 to flare or other disposal, as desired.

The following tabular data further describe and specify an embodiment of the invention.

Specific example Vapor feed (1):

Quantity, b./l1. (equivalent) 1,250

Temperature, F 900 Light cycle oil removal (3):

Quantity, b./h. 600

Moisture content, p.p.m 200 Initial boiling point, F. 430

Boiling range, F. 430-620 Light cycle oil product (9):

Quantity, b./h 590 Moisture content, ppm. 50

initial boiling point, F. 460

Boiling range, F. 460620 Seal oil (10):

Quantity, b./h. i

Moisture content, p.p.m 50

Initial boiling point, F 460 Boiling range 460-620 Used seal oil (11):

Quantity, b./h. 10

Moisture content, ppm 100 Initial boiling point, F. 440

Boiling range, F. 440-620 Tower 2:

Pressure, p.s.i.a 30

Bottom temperature, F 700 Top temperature, F. 225 Vessel 4:

Pressure, p.s.i.a

Temperature, F 430 Vacuum pump 5: Nash Engineering Companys Bulletin 367 (copyright 1945) describes a pump suitable for use in this operation.

In some operations, it may be desired to use more than one vacuum pump. That is, the dried and stabilized oil from the first vacuum stage is charged to a second vacuum stage wherein a second vacuum pump is used, and the final oil product, having been subjected to two vacuum operations, is used as the seal oil for both of the vacuum pumps.

Among the oils which can be processed according to the invention (any distillation column side stream product can be so processed) include kerosene, heating distillates, gas oils, light cycle oils, heavy cycle oils, etc. Other feed stocks which can be used as charge to the distillation column 2 include various crude oils, distillates from various crude distillations, as well as cracked efiiuents such as from thermal or catalytic cracking of various gas oils and/ or residuums, e.g., topped crude oil.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, the drawing and the appended claims to the invention the essence of which is that in a vacuum-stripping of an oil the stripped vases;

oil is used as seal oil for th acuurn pump or producing zone which produces the reduced pressure or vacuum with which the oil is stripped.

I claim:

1. An improved method of removing lighter hydrocarbons and water vapor from a stream of oil containing the same which comprises passing said stream of oil into a fractionation zone, fractionating said stream of oil in said fractionating zone, obtaining an overhead and a bottoms product, forming and recovering in said fractionating zone an intermediate oil str am, passing said intermediate oil stream to a zone maintained under stripping conditions and therein stripping said intermediate stream of oil to remove vapors therefrom, recovering overhead said vapors, drawing said vapors from said stripping zone employing a reduced pressure producing zone requiring a sealing fiuid, removing from said stripping zone stripped oil as a product of the operation, passing a portion of said product to said vacuum producing zone as sealing fluid therefor, discharging from said vacuum producing zone said vapors removed from said stripping Zone and passing into said vacuum producing zone and said sealing fluid used in said vacuum producing zone, and returning said vapors and said sealing fluid to said fractionation zone.

2. An improved method of removing lighter hydrocarbons and water vapor from a stream of oil containing the same which comprises passing said stream of oil into a fractionation zone, fractionating said stream of oil in said fractionating zone, obtaining an overhead and a bottoms product, forming and recovering in said fractionating zone an intermediate oil stream, passing said intermediate oil stream to a zone maintained under stripping conditions and therein stripping said intermediate stream of oil to remove vapors therefrom, passing a hydrocarbon gas stripping fluid into said stripping zone, recovering overhead said vapors, drawing said vapors from said stripping zone employing a reduced pressure producing zone requiring a sealing fluid, removing from said stripping zone stripped oil as a product of the operation, pass ing a portion of said product to said vacuum producing zone as sealing fluid therefor, discharging from said vacuum producing zone said vapors removed from said stripping zone and passing into said vacuum producing zone and said sealing fluid used in said vacuum producing zone, and returning said vapors and said sealing fluid to said fractionation zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,851,550 Tuttle Mar. 29, 1932 1,972,157 Miller Sept. 4, 1934 2,073,446 Ellsberg Mar. 9, 1937 FOREIGN PATENTS 781,505 Great Britain Aug. 21, 1957 OTHER REFERENCES Brown: Unit Operations, John Wiley and Sons, Inc., 1955, pp. 181, 182. 

1. AN IMPROVED METHOD OF REMOVING LIGHTER HYDROCARBONS AND WATER VAPOR FROM A STREAM OF OIL CONTAINING THE SAME WHICH COMPRISES PASSING SAID STREAM OF OIL INTO A FRACTIONATION ZONE, FRACTIONATING SAID STREAM OF OIL IN SAID FRACTIONATING ZONE, OBTAINING AN OVERHEAD AND A BOTTOMS PRODUCT, FORMING AND RECOVERING IN SAID FRACTIONATING ZONE AN INTERMEDIATE OIL STREAM, PASSING SAID INTERMEDIATE OIL STREAM TO A ZONE MAINTAINED UNDER STRIPPING CONDITIONS AND THEREIN STRIPPING SAID INTERMEDIATE STREAM OF OIL TO REMOVE VAPORS THEREFROM, RECOVERING OVERHEAD SAID VAPORS, DRAWING SAID VAPORS FROM SAID STRIPPING ZONE EMPLOYING A REDUCED PRESSURE PRODUCING ZONE REQUIRING A SEALING FLUID, REMOVING SAID STRIPPING ZONE STRIPPED OIL AS A PRODUCT OF THE OPERATION, PASSING A PORTION OF SAID PRODUCT TO SAID VACUUM PRODUCING ZONE AS SEALING FLUID THEREFOR, DISCHARGING FROM SAID VACUUM PRODUCING ZONE SAID VAPORS REMOVED FROM SAID STRIPPING ZONE AND PASSING INTO SAID VACUUM PRODUCING ZONE AND SAID SEALING FLUID USED IN SAID VACUUM PRODUCING ZONE, AND RETURNING SAID VAPORS AND SAID SEALING FLUID TO SAID FRACTIONATION ZONE. 